The present invention relates to wireless communications in general and, in particular, to a satellite communications network.
Broadband satellite services are gaining traction in North America. While such first generation satellite systems may provide multi-gigabit per second (Gbps) per satellite overall capacity, many current designs of such systems may inherently limit the number of customers who may be served with sufficient bandwidth. For example, because this capacity may be split across numerous coverage areas, the bandwidth to each user may be constrained. While existing designs have a number of capacity limitations, the demand for such broadband services continues to grow.
To meet such demands, multi-beams satellites may be used with Variable Coding and Modulation (VCM) or Adaptive Coding and Modulation (ACM). According to the message type and the link condition, VCM and ACM transmitters utilize codes of various rates and sizes and modulations of different orders. High rate codes and high order modulations are used to take advantage of favorable channel conditions, while low rate codes and low order modulations are used to ensure error free transmission when the channel conditions degrade.
Physical layer frame synchronization and physical layer header processing present difficult challenges in such an environment. In some instances, an identifier known at the receiver is included in a physical layer header to assist in identifying a start of a frame, and provide for frame synchronization. However, this solution may increase overhead because an identifier known at the receiver does not carry information. Physical layer header decoding can also present challenges. Modulation and coding can change on a per-frame basis, and information on the applicable format may be included in the physical layer header. Reliable and efficient physical layer header synchronization and decoding techniques may, therefore, be beneficial in a range of VCM and ACM systems.